This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-394352 filed on Dec. 26, 2001, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine such as an alternator or a starter motor for use in an automotive vehicle and to a method of manufacturing the same. More particularly, the present invention relates to a structure and a method for insulating conductors inserted into a slot of a core forming a rotor or a stator of a rotary electric machine.
2. Description of Related Art
A stator core of a rotary electric machine having conductor segments inserted into slots of the stator core in its axial direction has been known hitherto. Axial ends of the conductor segments are connected to one another forming a stator winding. For example, a method of manufacturing a stator having a stator winding formed by a plurality of U-shaped conductor segments is disclosed in JP-B2-3196738. The U-shaped conductor segment has a pair of conductors inserted into slots formed in a stator core. One conductor of the U-shaped conductor segment is inserted into one slot, while the other conductor is inserted into another slot which is apart from the one slot by a pole pitch. After plural conductor segments are all inserted into the slots, axial ends of conductors are connected to one another forming a stator winding.
JP-A-2001-37131 discloses a stator having a stator winding formed by plural L-shaped conductor segments. The L-shaped conductor segments are inserted into slots of the stator core from both axial ends thereof. Then, axial ends of the L-shaped conductor segments are electrically connected to one another to form a stator winding.
In such stators or rotors having the U-shaped or L-shaped conductor segments inserted in an axial direction of the stator core (referred to as a rotary electric machine having axially inserted conductors), a space factor for accommodating the conductors in a slot can be made higher, compared with a space factor in stators having a stator winding formed by winding a continuous wire. This is because conductor segments having a rectangular cross-section can be used in the stator using the U-shaped or L-shaped conductor segments. By improving the space factor in the slot, the rotary electric machine can be made compact in size and light in weight. Further, a rotary electric machine having a high output can be realized in a compact size.
In the rotary electric machine having axially inserted conductors, an insulation sleeve for electrically insulating the conductors from the core is inserted into each slot before the conductors are inserted. The insulation sleeve inserted into the slot tends to slide in its axial direction by a frictional force between the conductors and the insulation sleeve when the conductors are inserted into the insulation sleeve. Further, edges of the conductors may scratch the inner surface of the insulation sleeve, and thereby insulating ability of the insulation sleeve may be damaged.
In a rotary electric machine disclosed in JP-A-58-157349, an insulation sleeve made of a thermoplastic material having a widened end in a trumpet shape is used. The conductors are inserted into the insulation sleeve from the widened end. The widened end is formed by heating and deforming the end portion of the insulation sleeve. A neck portion of the widened end tends to become thin because the neck portion is strongly pressed against the edges of the slot due to a thrusting force given to the insulation sleeve by the conductors when the conductors are inserted into the insulation sleeve. If the neck portion becomes thin, the insulating ability of the sleeve is reduced.
To alleviate the contacting force between the neck portion of the widened end and the edges of the slot, the insulation sleeve may be pulled back in a direction opposite to a direction in which the conductors are inserted before inserting the conductors into the insulation sleeve, as disclosed in JP-A-2000-308314. However, there still remains a problem that the insulation ability at the neck portion is reduced, because it is difficult to maintain the pulled back position of the insulation sleeve against the thrusting force caused by insertion of the conductors.
The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an improved rotary electric machine, in which insulating ability of the insulation sleeve is not reduced by inserting conductors into the insulation sleeve. Another object of the present invention is to provide a method of manufacturing such an improved rotary electric machine.
The present invention is applicable to stator or rotor cores of various rotary electric machines. The present invention applied to a stator core of an alternator for use in an automotive vehicle will be described below as a representative example. The stator core is formed in a cylindrical shape, and a plurality of slots are formed along an inner bore of the stator core. An insulation sleeve, made of a thermoplastic resin material, having a substantially rectangular cross-section is inserted into each slot. Conductors forming a stator winding are inserted into the insulation sleeve. In other words, the conductors are electrically insulated from the stator core by the insulation sleeve.
The insulation sleeve includes four corner portions each contacting respective corners of the slot and flat portions positioned in parallel to sidewalls of the slot. When the insulation sleeve is inserted into the slot, the flat portions of the insulation sleeve are positioned apart from the sidewalls of the slot, forming certain spaces between the flat portions and the sidewalls. An inner space of the insulation sleeve is enlarged by inserting the conductors into the insulation sleeve, and thereby flat portions are brought into contact with the sidewalls of the slot, and the corner portions are further pressed against the corners of the slot.
Thus, the insulation sleeve is firmly kept in the slot, avoiding its movement in the longitudinal direction by insertion of the conductors. The insulation sleeve is protected from being damaged by its longitudinal slide in the slot. Accordingly, the conductors are properly insulated from the stator core by the insulation sleeve kept in the slot.
The insulation sleeve is made of a thermoplastic resin tape. Bending lines to be positioned at boundaries between the corner portions and flat portions are formed on the resin tape along its longitudinal direction. Then, the resin tape is folded into the shape of the insulation sleeve. Then, the folded resin tape is cut into an individual insulation sleeve having a predetermined length. The insulation sleeve thus formed is inserted into each slot of the stator core. Preferably, one end of the insulation sleeve from which the conductors are inserted is widened in a trumpet shape to facilitate easy insertion of the conductors.
According to the present invention, the insulation sleeve is prevented from sliding in the slot in the process of inserting the conductors into the insulation sleeve, and damages of the insulation sleeve due to its sliding in the slot are avoided.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.